In textile machines, such as carding machines and drawframes, it is frequently observed that periodic defects in the unit sliver weight, i.e. the weight per unit length, are created within the machine and which can be related to imperfections in particular rotating members of the machine such as a roller being out-of-round. Various evenness tests and frequency spectrographs have been previously employed to detect such defects.
Typically, no attempt is made to correct such defects short of replacing the defective component. As one known exception to the practice of replacing the component, a computer controlled sliver weight corrective system has been employed in which the speed of the doffer of a carding machine is adjusted square wave fashion, up and down between two set speeds, once per revolution of the doffer. In this computer control system, the angular position of the doffer is sensed and a program stored profile is built up relating the doffer position to the sliver weight at the time of sensing. This stored profile in the computer then directs the doffer speed to go up or down between the mentioned two set speeds. This system has the disadvantage of being dependent on the square wave form of correction, the further disadvantage of having to respond to the high inertia of the doffer, the disadvantage of being limited to two corrective speeds, and the disadvantage of having to periodically reset the two speeds. Thus, it has been known to attempt to correct for periodic variations in sliver weight by sensing and storing angular positions of a single relatively heavy rotating member, i.e. the doffer, and regulating its speed between two fixed speeds only in accordance with the measured unit weight of the sliver. However, it has not been known or recognized that a more efficient control of sliver weight could be obtained by regulating the speed of the feed roll, sensing the angular positions of plural rotating members and developing a control signal capable of regulating the feed roll speed so that such speed may be any of numerous speeds uniquely suited to the needed sliver weight correction.
An object of the present invention is that of providing a sliver weight corrective system and method which depends on using a computer or programmable controller for regulating the feed roll rather than the doffer and in a manner permitting a relatively wide range of speed changes.
Other objects will become apparent as the description proceeds.